The invention relates to an air conditioning system which increases the efficiency of the heating cycle when it operates in a location where the temperature remains above zero (0.degree. C.) and region where the daily temperature variation is severe.
Conventional air conditioning systems are illustrated in FIGS. 1 and 2, which illustrate a heat pump and a refrigerant heating type air conditioner, respectively. The cooling operation of these air conditioners is performed when a high temperature, high pressure refrigerant gas discharged from a compressor 1 flows into an outdoor heat-exchanger 2 in the direction of the solid line arrows. The refrigerant gas is condensed at the outdoor heat-exchanger, i.e. the condenser, and changed into a high pressure liquid phase refrigerant, and then it flows into an expansion tube 3.
The high pressure liquid refrigerant is transformed into a low temperature, low pressure liquid refrigerant by the effect caused by the expansion tube 3, and then it flows into an indoor heat-exchanger 4, i.e. the evaporator. At the evaporator, the liquid refrigerant is changed into a low temperature, low pressure gaseous refrigerant and finally it flows back to the compressor 1. By repeating the above cycle, the cooling operation is performed.
In the heating mode, shown in FIG. 1, performed by a heat pump type air conditioner, a high temperature, high pressure gaseous refrigerant is discharged from a compressor 1 and flows into an indoor heat-exchanger 4 in the direction of the broken line arrows. The gas is condensed at the indoor heat-exchanger 4 and then heat is dispersed by air introduced from the indoor location by cross fan 5. The air then flows to the desired indoor location to perform the heating function. Further, a high pressure liquid refrigerant then flows into an expansion tube 3.
The high pressure liquid refrigerant is transformed into a low temperature, low pressure liquid refrigerant by the effect caused by the expansion tube 3, and then it flows into an outdoor heat-exchanger 2, i.e. the evaporator. At the evaporator, the liquid refrigerant is changed into a low temperature, low pressure gaseous refrigerant and finally it flows back to the compressor 1.
However, because the compressor employed in of the above described air conditioner may have a larger capacity than is needed during the heating cycle, there is a problem in that excessive power consumption is required. Furthermore, because the outdoor environmental temperature is low, the liquid refrigerant insufficiently heat-exchanges at the indoor heat exchanger. The refrigerant directed to a compressor consists of a large amount of liquid, and thus the heating efficiency is decreased. For example, when the outdoor temperature is under 50.degree. C. the full effect of the heating operation is seldom attained.
To perform the heat-exchange operation regardless of the above described drop in the outdoor temperature, a refrigerant heating type air conditioner using prior art is shown in FIG. 2.
In an auxiliary heating mode, performed according to the air conditioner of FIG. 2, a high temperature refrigerant heated by a heater 7 flows into a compressor 1 and then into an indoor heat-exchanger 4 in the direction of the broken line arrows. The indoor heat-exchanger, i.e. the condenser, receives the refrigerant to be condensed. At the condenser the indoor air drawn by a cross fan 5 is heat-exchanged. The heat exchanged air is blown to the indoor space to achieve the desired heating effect. Further, a liquid refrigerant under high temperature flows back to the heater 7. Numeral 18 is the refrigerant tube. The typical refrigerant heating type air conditioner is disclosed in Japanese Patent Publication No.1987-62278.
However, even in a location where the temperature is above zero and the daily temperature variations are severe, a compressor located on the main refrigerant tube may be employed to perform the main heating function in this type of air conditioner. When the air conditioner is employed for the auxiliary heating function in the above described location, the compressor may have an excessive capacity, thereby decreasing the efficiency of the system.